Consider hard-coding v2 upgrade heights

[rootulp]

Context

We used a --v2-upgrade-height flag on networks

Problem

If a consensus node is block syncing from genesis, it needs to provide the --v2-upgrade-height

Proposal

Consider hard-coding the --v2-upgrade-heights for arabica, mocha, mainnet beta so that node operators don't have to specify it.

[cmwaters]

I am for this

[rootulp]

Note: this will be cumbersome to test b/c we'll need to block sync on Arabica, Mocha, or Mainnet through the v2 upgrade height.

To make this issue easier, we should build a utility that makes it easier + faster to block sync.